<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>
  <body>
    <script>
      function fn() {
        console.log(1);
        Promise.resolve().then(function () {
          console.log(2);
        });
      }

      setTimeout(function () {
        console.log(3);
        Promise.resolve().then(fn);
      }, 1000);

      Promise.resolve().then(function () {
        console.log(4);
      });

      console.log(5);
    </script>
  </body>
</html>
